This paper deals with a production scheduling problem that typically occurs in the aeronautics industry involving special structures called assembly fixtures, composed of several workstations in parallel, which are used to assemble the parts of the aircrafts. Tasks should be scheduled to be performed in these workstations in order to minimize the make-span; however, in addition to the usual constraints, such as due dates and tasks priority, there are also limitations that prevent two tasks from being performed at the same time, in two adjacent workstations on the assembly fixture. A mixed integer model to represent the problem was proposed based on practical case studies of assembly fixtures schedules of an aeronautic company. The solutions generated by the model were implemented, in practice, with gains both in the use of the assembly fixtures studied, as well as in the use of the required labor.